PeerStreamer

/*

 * Common code between the AC-3 encoder and decoder

 * Copyright (c) 2000 Fabrice Bellard

 *

 * This file is part of Libav.

 *

 * Libav is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * Libav is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with Libav; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

/**

 * @file

 * Common code between the AC-3 encoder and decoder.

 */

#include "avcodec.h"

#include "ac3.h"

#include "get_bits.h"

/**

 * Starting frequency coefficient bin for each critical band.

 */

const uint8_t ff_ac3_band_start_tab[AC3_CRITICAL_BANDS+1] = {

      0,  1,   2,   3,   4,   5,   6,   7,   8,   9,

     10,  11, 12,  13,  14,  15,  16,  17,  18,  19,

     20,  21, 22,  23,  24,  25,  26,  27,  28,  31,

     34,  37, 40,  43,  46,  49,  55,  61,  67,  73,

     79,  85, 97, 109, 121, 133, 157, 181, 205, 229, 253

};

#if CONFIG_HARDCODED_TABLES

/**

 * Map each frequency coefficient bin to the critical band that contains it.

 */

const uint8_t ff_ac3_bin_to_band_tab[253] = {

     0,

     1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12,

    13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,

    25, 26, 27, 28, 28, 28, 29, 29, 29, 30, 30, 30,

    31, 31, 31, 32, 32, 32, 33, 33, 33, 34, 34, 34,

    35, 35, 35, 35, 35, 35, 36, 36, 36, 36, 36, 36,

    37, 37, 37, 37, 37, 37, 38, 38, 38, 38, 38, 38,

    39, 39, 39, 39, 39, 39, 40, 40, 40, 40, 40, 40,

    41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41,

    42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42,

    43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43,

    44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44,

    45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45,

    45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45,

    46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46,

    46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46,

    47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47,

    47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47,

    48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48,

    48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48,

    49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49,

    49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49

};

#else /* CONFIG_HARDCODED_TABLES */

uint8_t ff_ac3_bin_to_band_tab[253];

#endif

static inline int calc_lowcomp1(int a, int b0, int b1, int c)

{

    if ((b0 + 256) == b1) {

        a = c;

    } else if (b0 > b1) {

        a = FFMAX(a - 64, 0);

    }

    return a;

}

static inline int calc_lowcomp(int a, int b0, int b1, int bin)

{

    if (bin < 7) {

        return calc_lowcomp1(a, b0, b1, 384);

    } else if (bin < 20) {

        return calc_lowcomp1(a, b0, b1, 320);

    } else {

        return FFMAX(a - 128, 0);

    }

}

void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,

                               int16_t *band_psd)

{

    int bin, band;

    /* exponent mapping to PSD */

    for (bin = start; bin < end; bin++) {

        psd[bin]=(3072 - (exp[bin] << 7));

    }

    /* PSD integration */

    bin  = start;

    band = ff_ac3_bin_to_band_tab[start];

    do {

        int v = psd[bin++];

        int band_end = FFMIN(ff_ac3_band_start_tab[band+1], end);

        for (; bin < band_end; bin++) {

            int max = FFMAX(v, psd[bin]);

            /* logadd */

            int adr = FFMIN(max - ((v + psd[bin] + 1) >> 1), 255);

            v = max + ff_ac3_log_add_tab[adr];

        }

        band_psd[band++] = v;

    } while (end > ff_ac3_band_start_tab[band]);

}

int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,

                               int start, int end, int fast_gain, int is_lfe,

                               int dba_mode, int dba_nsegs, uint8_t *dba_offsets,

                               uint8_t *dba_lengths, uint8_t *dba_values,

                               int16_t *mask)

{

    int16_t excite[AC3_CRITICAL_BANDS]; /* excitation */

    int band;

    int band_start, band_end, begin, end1;

    int lowcomp, fastleak, slowleak;

    /* excitation function */

    band_start = ff_ac3_bin_to_band_tab[start];

    band_end   = ff_ac3_bin_to_band_tab[end-1] + 1;

    if (band_start == 0) {

        lowcomp = 0;

        lowcomp = calc_lowcomp1(lowcomp, band_psd[0], band_psd[1], 384);

        excite[0] = band_psd[0] - fast_gain - lowcomp;

        lowcomp = calc_lowcomp1(lowcomp, band_psd[1], band_psd[2], 384);

        excite[1] = band_psd[1] - fast_gain - lowcomp;

        begin = 7;

        for (band = 2; band < 7; band++) {

            if (!(is_lfe && band == 6))

                lowcomp = calc_lowcomp1(lowcomp, band_psd[band], band_psd[band+1], 384);

            fastleak = band_psd[band] - fast_gain;

            slowleak = band_psd[band] - s->slow_gain;

            excite[band] = fastleak - lowcomp;

            if (!(is_lfe && band == 6)) {

                if (band_psd[band] <= band_psd[band+1]) {

                    begin = band + 1;

                    break;

                }

            }

        }

        end1 = FFMIN(band_end, 22);

        for (band = begin; band < end1; band++) {

            if (!(is_lfe && band == 6))

                lowcomp = calc_lowcomp(lowcomp, band_psd[band], band_psd[band+1], band);

            fastleak = FFMAX(fastleak - s->fast_decay, band_psd[band] - fast_gain);

            slowleak = FFMAX(slowleak - s->slow_decay, band_psd[band] - s->slow_gain);

            excite[band] = FFMAX(fastleak - lowcomp, slowleak);

        }

        begin = 22;

    } else {

        /* coupling channel */

        begin = band_start;

        fastleak = (s->cpl_fast_leak << 8) + 768;

        slowleak = (s->cpl_slow_leak << 8) + 768;

    }

    for (band = begin; band < band_end; band++) {

        fastleak = FFMAX(fastleak - s->fast_decay, band_psd[band] - fast_gain);

        slowleak = FFMAX(slowleak - s->slow_decay, band_psd[band] - s->slow_gain);

        excite[band] = FFMAX(fastleak, slowleak);

    }

    /* compute masking curve */

    for (band = band_start; band < band_end; band++) {

        int tmp = s->db_per_bit - band_psd[band];

        if (tmp > 0) {

            excite[band] += tmp >> 2;

        }

        mask[band] = FFMAX(ff_ac3_hearing_threshold_tab[band >> s->sr_shift][s->sr_code], excite[band]);

    }

    /* delta bit allocation */

    if (dba_mode == DBA_REUSE || dba_mode == DBA_NEW) {

        int i, seg, delta;

        if (dba_nsegs > 8)

            return -1;

        band = band_start;

        for (seg = 0; seg < dba_nsegs; seg++) {

            band += dba_offsets[seg];

            if (band >= AC3_CRITICAL_BANDS || dba_lengths[seg] > AC3_CRITICAL_BANDS-band)

                return -1;

            if (dba_values[seg] >= 4) {

                delta = (dba_values[seg] - 3) << 7;

            } else {

                delta = (dba_values[seg] - 4) << 7;

            }

            for (i = 0; i < dba_lengths[seg]; i++) {

                mask[band++] += delta;

            }

        }

    }

    return 0;

}

/**

 * Initialize some tables.

 * note: This function must remain thread safe because it is called by the

 *       AVParser init code.

 */

av_cold void ff_ac3_common_init(void)

{

#if !CONFIG_HARDCODED_TABLES

    /* compute ff_ac3_bin_to_band_tab from ff_ac3_band_start_tab */

    int bin = 0, band;

    for (band = 0; band < AC3_CRITICAL_BANDS; band++) {

        int band_end = ff_ac3_band_start_tab[band+1];

        while (bin < band_end)

            ff_ac3_bin_to_band_tab[bin++] = band;

    }

#endif /* !CONFIG_HARDCODED_TABLES */

}